Study of the synergistic role of multivalence states of 3d cations on the crystal lattice distortion and magnetic behavior of Sr2FeCoO6-d: A spectroscopic study

In perovskite oxides, the multiple charge states of cations influence their local structure and correlated physical properties. In this report, we studied the role of multivalence cations on the local structure and magnetic behavior of the oxygen-deficient system Sr2FeCoO6-& delta; (SFCO), prepared by the solid-state synthesis technique. A detailed structural and geometrical analysis confirmed the coexistence of orthorhombic (Brownmillerite) and cubic crystal symmetries and a gesture of the Jahn-Teller (JT) distortion. The intense Raman modes are allowed to be indexed for BO-polyhedra and JT-distortion. Experimental and theoretical analysis of the X-ray photoelectron spectroscopy (XPS) spectra supported the mixed oxidation state of Fe (Fe3+/Fe4+) and Co (Co2+/Co3+), further confirmed by theoretically simulated X-ray absorption spectroscopy (XAS) spectra. The presence of the multivalence states leads to AFM/FM exchange interaction in the sample which further leads to glassy magnetic behavior.